Suxamethonium and hyperkalaemia

Electrolyte Disturbances Related to Sodium and Potassium and Electroconvulsive Therapy: A Systematic Review

INTRODUCTION

Electrolyte disturbances related to sodium and potassium affect patients with mental disorders undergoing electroconvulsive therapy (ECT). The objective of this study was to systematically summarize the data regarding ECT and electrolyte disturbances related to sodium and potassium.

MATERIALS AND METHODS

A systematic literature review in accordance with PRISMA guidelines was conducted. Clinical studies of patients receiving ECT with electrolyte disturbances reported before or after treatment were included.

RESULTS

We identified nine case reports and two retrospective studies describing electrolyte abnormalities occurring before or after ECT. ECT was effective and safe in patients with hyponatremia and hypernatremia, including the elderly patient population. This treatment was also effective in treating psychiatric symptoms that may persist after ionic equalization. Electrolyte disturbances after ECT were rare. Reports have suggested that succinylcholine used as a muscle relaxant was the main cause of hyperkalemia after ECT.

CONCLUSIONS

Electrolyte control is a crucial aspect of guiding ECT therapy. In the context of sodium-related disorders, it is critical to control patient hydration as part of therapy. In addition, succinylcholine should not be used in patients with immobilization, such as catatonia or neuroleptic malignant syndrome. It is necessary to conduct further studies to clarify whether electrolyte concentration affects ECT parameters and clinical efficacy. In addition, it is necessary to assess the influence of various anesthetics on these conditions during ECT. The result of this review should be interpreted bearing in mind the small number of studies conducted to date and the low quality of the evidence they provide.

Spinal neuraxial anaesthesia for Caesarean section in a parturient with Type I Arnold–Chiari malformation and syringomyelia

Type 1 Arnold–Chiari Malformation is associated with prolapse of the cerebellar tonsils into or below the level of the foramen magnum and is usually diagnosed in adults. There are no current guidelines for the management of patients with a residual Type I Arnold–Chiari Malformation, planned for a Caesarean section under spinal neuraxial anaesthesia. The paucity of literature on this topic presents as a management dilemma. We report a case of a term parturient with Type 1 Arnold–Chiari Malformation, following surgical decompression four years earlier, with a residual syringomyelia who underwent an elective Caesarean section under spinal neuraxial anaesthesia. This case highlights that multidisciplinary management and an early anaesthetic consult is of paramount importance in the outcome of the patient, and that spinal neuraxial anaesthesia can be considered as a safe anaesthetic option.

Rapid Sequence Induction and Intubation

The modern version of RSI starts with preoxygenation. General anaesthesia is then induced using a rapid acting intravenous anaesthetic and a rapid acing muscle relaxant. Cricoid pressure is applied by an experienced assistant during induction, which should then be maintained until the trachea of the patient is intubated, correct positioning of the tracheal tube confirmed and the cuff inflated. The patient is conventionally not ventilated during this phase but critically ill patients are exceptions. The patient's tracheal should be intubated when adequately paralysed and its position verified. The assistant can then relieve the cricoid pressure and the tracheal tube fixed.

Emergency medicine evaluation and management of the end stage renal disease patient

BACKGROUND

End stage renal disease (ESRD) is increasing in the U.S., and these patients demonstrate greater all-cause mortality, cardiovascular events, and hospitalization rates when compared to those with normal renal function. These patients may experience significant complications associated with loss of renal function and dialysis.

OBJECTIVE

This review evaluates complications of ESRD including cardiopulmonary, neurologic, infectious disease, vascular, and access site complications, as well as medication use in this population.

DISCUSSION

ESRD incidence is rapidly increasing, and patients commonly require renal replacement therapy including hemodialysis (HDS) or peritoneal dialysis (PD), each type with specific features. These patients possess greater risk of neurologic complications, cardiopulmonary pathology, infection, and access site complications. Focused history and physical examination are essential. Neurologic issues include uremic encephalopathy, cerebrovascular pathology, and several others. Cardiopulmonary complications include pericarditis, pericardial effusion/tamponade, acute coronary syndrome, sudden cardiac death, electrolyte abnormalities, pulmonary edema, and air embolism. Infections are common, with patients more commonly presenting in atypical fashion. Access site infections and metastatic infections must be treated aggressively. Access site complications include bleeding, aneurysm/pseudoaneurysm, thrombosis/stenosis, and arterial steal syndrome. Specific medication considerations are required for analgesics, sedatives, neuromuscular blocking agents, antimicrobials, and anticoagulants.

CONCLUSIONS

Consideration of renal physiology with complications in ESRD can assist emergency providers in the evaluation and management of these patients. ESRD affects many organ systems, and specific pharmacologic considerations are required.

Perioperative Pharmacologic Management of Patients with End Stage Renal Disease

The pharmacokinetics of numerous medications used in the perioperative period are altered in patients with end-stage renal disease. Clearance of drugs, or their metabolites, that are normally excreted by the kidney is markedly reduced in ESRD. In addition, patients with ESRD may also have alterations in gastrointestinal absorption, volume of distribution, protein binding, and metabolic clearance of pharmacologic agents. Finally, drug removal may be augmented during dialysis. All of these factors contribute to the need for dose adjustment of medications, including analgesics, anesthetics, neuromuscular blockers, and antimicrobial agents, which may be used in the perioperative management of the ESRD patient.

Cardiac arrest and succinylcholine-induced hyperkalemia in a patient with a triton tumor

We report a case of succinylcholine-induced hyperkalemia in a patient with a mediastinal triton tumor, which is characterized by a rhabdomyosarcomatous differentiation. Caution should be taken with succinylcholine use in patients presenting with a rhabdomyosarcomatous tumor or with a tumor of unknown cell type when histopathological diagnosis is not available.

The kalaemic and neuromuscular effects of succinylcholine in centronuclear myopathy: A pilot investigation in a canine model

BACKGROUND

Myopathies are generally considered to increase the risk for succinylcholine-induced hyperkalaemia and may affect the duration of action of neuromuscular blockers. Centronuclear (myotubular) myopathy (CNM) is congenital and produces various degrees of muscular weakness and associated complications such as respiratory failure. The effects of succinylcholine and the potentially lethal consequences of hyperkalaemia on patients with CNM are unknown due to its rarity. One source of information is the dog, as CNM occurs naturally in dogs. Because of its remarkable similarity with the disease in man, canine CNM can serve as a model to further our knowledge of the effects of succinylcholine.

OBJECTIVES

We examined the kalaemic and neuromuscular effects of succinylcholine in dogs with and without autosomal-recessive CNM.

DESIGN

A prospective, experimental study.

SETTING

Anaesthesiology laboratory, College of Veterinary Medicine, Cornell University, New York, USA.

PATIENTS

Six dogs with autosomal-recessive CNM and six control dogs.

INTERVENTIONS

Dogs received succinylcholine 0.3 mg kg during isoflurane anaesthesia.

MAIN OUTCOME MEASURES

Whole blood potassium concentration was measured 5 min before and after succinylcholine administration. Neuromuscular function was measured with acceleromyography and single twitch stimulation.

RESULTS

All dogs recovered uneventfully from anaesthesia. The increase in potassium concentration [mean (SD)] following succinylcholine was similar between groups: CNM 0.5 (0.4) mmol l and control 0.7 (0.4) mmol l (P = 0.47). Recovery of the single twitch to 25, 75 and 90% was longer in the CNM group (all P < 0.001); 90% recovery took 35.5 (1.18) min for the CNM group and 23.3 (1.68) min for the control group.

CONCLUSION

CNM did not exacerbate the increase in blood potassium that is ordinarily seen with succinylcholine. Recovery from succinylcholine was nearly 50% longer in dogs with CNM. Although our sample size is too small to evaluate the incidence of succinylcholine-induced hyperkalaemia, extrapolation of these findings suggests that increased duration of action should be expected if succinylcholine is given to a patient with autosomal-recessive CNM.

Anesthetic management during Cesarean section in a woman with residual Arnold-Chiari malformation Type I, cervical kyphosis, and syringomyelia

Background:

Type I Arnold–Chiari malformation (ACM) has an adult onset and consists of a downward displacement of the cerebellar tonsils and the medulla through the foramen magnum. There is paucity of literature on the anesthetic management during pregnancy of residual ACM Type I, with cervical xyphosis and persistent syringomyelia.

Case Description:

A 34-year-old woman with surgically corrected ACM Type I presented for Cesarean delivery. A recent MRI demonstrated worsening of cervical xyphosis after several laminectomies and residual syringomyelia besides syringopleural shunt. Awake fiberoptic intubation was performed under generous topical anesthesia to minimize head and neck movement during endotracheal intubation. We used a multimodal general anesthesia without neuromuscular blockade. The neck was maintained in a neutral position. Following delivery, the patient completely recovered in post-anesthesia care unit (PACU), with no headache and no exacerbation or worsening of neurological function.

Conclusions:

The present case demonstrates that patients with partially corrected ACM, syringomyelia, cervical kyphosis, and difficult intubation undergoing Cesarean delivery require an interdisciplinary team approach, diligent preparation, and skilled physicians.

Management of the dialysis patient in general intensive care

The incidence of end-stage renal disease (ESRD) is rising and represents an important group of patients admitted to intensive care units (ICU). ESRD patients have significant co-morbidities and specific medical requirements. Renal replacement therapy (RRT), cardiovascular disease, disorders of electrolytes, drug metabolism, and sepsis are discussed. This review provides a practical approach to problems specific to the ESRD patient and common problems on ICU that require special consideration in ESRD patients. ESRD patients are at risk of hyperkalaemia. I.V. insulin and nebulized salbutamol lower serum potassium until definitive treatment with RRT is instituted. ESRD patients are prone to hypocalcaemia, which requires i.v. replacement if associated with complications. Midazolam has delayed metabolism and elimination in renal impairment and should be avoided. Morphine and its derivatives accumulate in renal failure and shorter-acting opiates are preferable. The use of diuretics is limited to patients with residual urine output. When required, therapeutic systemic anticoagulation should be achieved with unfractionated heparin as it is reversible and its metabolism and clearance are independent of renal function. The risk of sepsis is higher among ESRD patients when compared with patients with normal renal function. Empiric treatment should include both Gram-positive and Gram-negative cover, and methicillin-resistant Staphylococcus aureus cover if the patient has a dialysis catheter. Cardiovascular events account for the majority of deaths among ESRD patients. Troponin-I and CK-MB in combination should be used as markers of acute myocardial damage in the appropriate context, whereas B-type natriuretic peptide and troponin-T values are of less value.

Analytic reviews: managing the agitated patient in the ICU: sedation, analgesia, and neuromuscular blockade

Physical and psychological distress is exceedingly common among critically ill patients and manifests generically as agitation. The dangers of over- and undertreatment of agitation have been well described, and the intensive care unit (ICU) physician must strike a balance in the fast-paced, dynamic ICU environment. Identification of common reversible etiologies for distress may obviate the need for pharmacologic therapy, but most patients receive some combination of sedative, analgesic, and neuroleptic medications during the course of their critical illness. As such, understanding key pharmacologic features of commonly used agents is critical. Structured protocols and objective assessment tools can optimize drug delivery and may ultimately improve patient outcomes by reducing ventilator days, ICU length of stay, and by reducing cognitive dysfunction.

Electrolyte disturbances associated with commonly prescribed medications in the intensive care unit

Electrolyte imbalances are common in critically ill patients. Although multiple disease states typically encountered in the intensive care unit may be responsible for the development of electrolyte disorders, medications may contribute to these disturbances as well. Medications can interfere with the absorption of electrolytes, alter hormonal responses affecting homeostasis, as well as directly impact organ function responsible for maintaining electrolyte balance. The focus on this review is to identify commonly prescribed medications in the intensive care unit and potential electrolyte disturbances that may occur as a result of their use. This review will also discuss the postulated mechanisms associated with these drug-induced disorders. The specific drug-induced electrolyte disorders discussed in this review involve abnormalities in sodium, potassium, calcium, phosphate, and magnesium. Clinicians encountering electrolyte disturbances should be vigilant in monitoring the patient's medications as a potential etiology. Insight into these drug-induced disorders should allow the clinician to provide optimal medical management for the critically ill patient, thus improving overall healthcare outcomes.

Anaesthesia for the obstetric patient with (non-obstetric) systemic disease

The number of women with serious (non-obstetric) systemic diseases achieving pregnancy and requiring obstetric anaesthetic management is increasing. The conditions that are most likely to cause maternal morbidity and mortality are cardiac disease, respiratory disease, neuromuscular disease, haematological disease, connective and metabolic diseases and psychiatric conditions including substance abuse. This article discusses the anaesthetic management of the pregnant mother with such serious systemic diseases.

Anaesthesia for renal transplant surgery

Renal transplantation is the preferred therapeutic option for patients with end-stage renal disease. Survival rates are much higher in patients who receive a transplant. Patients with renal failure have significant concomitant medical conditions, such as cardiovascular disease. This article provides an overview of the important issues to be considered in patients undergoing renal transplant, and discusses the anaesthetic management of these patients.

Suxamethonium-induced hyperkalaemia 6 weeks after chemoradiotherapy in a patient with rectal carcinoma

Suxamethonium causes an efflux of potassium (K+) ions by depolarizing acetylcholine receptors within the neuromuscular junction and produces a transient, small rise in serum K+ concentration in normal individuals that is usually of little clinical importance. Despite the clear efficacy and relative safety of suxamethonium in many patients, anaesthetists are also very aware that acute, severe hyperkalaemia resulting in important cardiovascular sequelae (e.g. malignant ventricular arrhythmias, cardiac arrest) may also occur with administration of suxamethonium in susceptible patients, including those with skeletal muscle injury or thermal trauma. In the current report, we describe a patient with rectal cancer initially treated with chemoradiotherapy who developed hyperkalaemia after suxamethonium and further discuss the potential factors that contributed to this response.

[Spontaneous spinal epidural haematoma during pregnancy]

Spontaneous spinal epidural haematomas are quite rare. We report here the case of a 27-year-old woman, without previous history of relevant medical disorder, who presented with acute paraplegia at 36 weeks of gestation. MRI performed in emergency revealed a T8 epidural haematoma. The management consisted in an emergency Caesarean section under general anaesthesia, followed immediately by a T8 laminectomy allowing the spinal cord decompression 14 hours after the first symptoms. Neurologic recovery was rapid and complete, except for bladder dysfunction persisting one month later. Spontaneous spinal epidural haematomas require a prompt diagnosis because neurologic prognosis essentially depends on the interval of time between onset of symptoms and surgical decompression. Obstetrical management especially depends on the term of pregnancy. For the anaesthesiologist, the difficulty is the management of both pregnant condition (full stomach general anaesthesia) and spinal cord compression (maintenance of spinal cord perfusion pression and limitation of ischaemia and oedema).

Airway Management in Critical Illness

Airway management in the ICU can be complicated due to many factors including the limited physiologic reserve of the patient. As a consequence, the likelihood of difficult mask ventilation and intubation increases. The incidence of failed airways and of cardiac arrest related to airway instrumentation in the ICU is much higher than that of elective intubations performed in the operating room. A thorough working knowledge of the devices available for the management of the difficult airway and recommended rescue strategies is paramount in avoiding bad patient outcomes. In this review, we will provide a conceptual framework for airway assessment, with an emphasis on assessment of the patient with limited cervical spine movement or injury and of morbidly obese patients. Furthermore, we will review the devices that are available for airway management in the ICU, and discuss controversies surrounding interventions like cricoid pressure and the use of muscle relaxants in the critically ill patient. Finally, strategies for the safe extubation of patients with known difficult airways will be provided.

Complications of anaesthesia in neuromuscular disorders

The purpose of this review is to alert non-anaesthesiologists to the various complications from which patients with neuromuscular disorders and those susceptible to malignant hyperthermia can suffer during anaesthesia. The patient's outcome correlates with the quality of consultation between anaesthesiologists, surgeons, neurologists and cardiologists. Special precautions must be taken, since many anaesthetics and muscle relaxants can aggravate the clinical features or trigger life-threatening reactions. Complications frequently occur in these patients, although anaesthetic procedures have become safer by the reduced administration of suxamethonium and the use of total intravenous anaesthesia, new volatile anaesthetics and non-depolarising relaxants. This review provides a synopsis of pre-operative anaesthetic considerations and adverse drug effects on skeletal, cardiac and smooth muscle tissue. It describes the pathogenetic aspects of typical complications and introduces anaesthetic procedures for the various neuromuscular disorders, including regional anaesthesia for patients in whom a restriction of respiratory and/or cardiac function is predicted.

[Primary treatment of burn patients]

Burn injuries can be caused by thermal, electrical, chemical, or mechanical trauma or radiation and are relatively rare, as they represent only about 1% of all emergencies. They are caused by accidents at home, during recreational activities, or in the occupational environment. Minor burn traumas are much more common than severe burn injuries with their systemic and potentially life-threatening effects. Altogether, these circumstances may result in a lack of routine for treating such injuries properly by physicians and their colleagues in the emergency room or intensive care unit. A clearly outlined concept for preclinical and clinical treatment can be the keystone of successful further clinical progress. The following article summarizes the current guidelines for first medical aid at the injury scene, burn stabilization and assessment in the emergency room, and the interdisciplinary approach for further clinical care. The treatment of dermatologic emergencies (acute epidermolytic syndromes) or caustic injuries by chemical agents is similar to the treatment of burn victims in many aspects but must be adapted in selected cases.

Perioperative management of patients with chronic kidney disease or ESRD

The perioperative management of patients with chronic kidney disease (CKD) or dialysis-dependent end-stage renal disease (ESRD) is complicated by both the underlying renal dysfunction, with associated disturbances of fluid and electrolyte homeostasis and altered drug clearance, and the presence of associated co-morbid conditions, including diabetes mellitus, chronic hypertension and cardiovascular and cerebrovascular disease. The impact of CKD on fluid and electrolyte management, haematological and cardiovascular complications and drug management in the perioperative period are reviewed. Special issues related to the management of haemodialysis and peritoneal dialysis patients in the perioperative period are also reviewed.

The pulmonary physician in critical care. 11: critical care management of respiratory failure resulting from COPD

Survival to hospital discharge of patients suffering exacerbations of COPD is better than other medical causes for ICU admission. Although non-invasive ventilation (NIV) may prevent progression to tracheal intubation, its failure in most cases should lead to a period of controlled mechanical ventilation aiming for early extubation, possibly supported by NIV and tracheostomy if this fails. A greater understanding of the physiological principles behind ventilatory support of patients with COPD should reduce patient-ventilator disharmony and avoid the excessive use of sedation. The risk of nosocomial infection increases with the length of time the patient remains in the ICU and commonly further prolongs the period of ventilator dependency. Weaning centres with an emphasis on general rehabilitation may offer the best support for such individuals.

Can succinylcholine be used safely in hyperkalemic patients?

The use of succinylcholine in hyperkalemic patients (serum potassium >5.5 mEq/L) is often viewed as relatively contraindicated, although there are no systematic data to define what preoperative potassium level is safe. We retrospectively reviewed more than 40,000 general anesthetics administered over 70 mo in which succinylcholine was given at the induction. This search yielded 38 patients with a preoperative potassium of 5.6 mEq/L or greater. Survival of the anesthetic was 100%, and no dysrhythmias or other major morbidity were documented upon manual review of the intraoperative automated record keeper charts or the patient medical records. These data allow a 95% confidence interval assessment of maximal risk for an event of 7.9%, which is not negligible, but which almost certainly grossly overestimates the risk for patients with moderately increased potassium levels. A prospective trial to definitively assess the safety margin for succinylcholine use in hyperkalemic patients would be difficult. Therefore, these data, taken in the context of a compelling case for rapid intubating conditions without long-term paralysis, suggest safety in succinylcholine use in patients with modest hyperkalemia.

IMPLICATIONS

In a review of more than 40,000 general anesthetics in which succinylcholine was given at induction, 38 patients had a preoperative potassium of 5.6 mEq/L or greater. All patients survived the anesthetic with no dysrhythmias or other major morbidity documented. Succinylcholine may be appropriate and safe for use in certain patients with moderate hyperkalemia.

Succinylcholine-induced hyperkalemia in a patient with mucositis secondary to chemotherapy

OBJECTIVE

To report a case of fatal hyperkalemia owing to succinylcholine administration in a patient with mucositis secondary to chemotherapy.

DESIGN

Case report.

SETTING

Adult intensive care unit (ICU) at Dartmouth-Hitchcock Medical Center.

PATIENTS

One patient with mucositis secondary to chemotherapy.

MEASUREMENTS AND MAIN RESULTS

A 37-yr-old female with recently diagnosed acute myelogenous leukemia was admitted to the ICU with mental status changes and progressive dyspnea requiring intubation and mechanical ventilation. Before ICU admission, the patient had suffered from painful mucositis causing severe dysphagia and bleeding, which was thought to be the result of chemotherapy. By the 10th ICU day, the patient's respiratory and mental status improved and the patient was successfully extubated. However, 8 hrs after extubation, she gradually developed severe respiratory distress, requiring reintubation and mechanical ventilation. The patient was given 14 mg of etomidate and 100 mg of succinylcholine intravenously. Immediately after the intubation, she suffered cardiac arrest. Her serum potassium level was 13.1 mEq/L and HCO3- was 16 mEq/L. The resuscitation attempt was unsuccessful, and the patient was pronounced dead.

CONCLUSION

Oral mucositis is a frequent and potentially severe complication of cancer chemotherapy. We believe that mucositis was a contributing factor to this case of fatal hyperkalemia after administration of succinylcholine, with a mechanism similar to that reported with thermal injury. Only nondepolarizing muscle relaxants should be used in patients who are at risk for mucositis. Mucositis should be added to the list of conditions in which succinylcholine is contraindicated.

Is succinylcholine appropriate or obsolete in the intensive care unit?

Muscle relaxants in intensive care unit (ICU) patients are predominantly administered to facilitate intubation. The adverse effect profile of succinylcholine is such that its use in the ICU must be considered obsolete. Suitable alternatives are the intermediately long-acting nondepolarizing relaxants, of which rocuronium is probably preferable.

Succinylcholine-induced hyperkalemia and rhabdomyolysis in a patient with necrotizing pancreatitis

IMPLICATIONS

Commonly used muscle relaxants may have serious side effects when used in critically ill patients. This case report relates some of these side effects and reviews the mechanisms by which they are thought to occur.

Drug-induced hyperkalemia: old culprits and new offenders

Prescribed medications, over-the-counter drugs, and nutritional supplements are used by many patients. Although most of these products are well tolerated, drug-induced hyperkalemia may develop in patients with underlying renal impairment or other abnormalities in potassium handling. Drug-induced hyperkalemia most often occurs from impaired renal potassium excretion. However, disturbed cellular uptake of a potassium load as well as excessive ingestion or infusion of potassium-containing substances may also occur. Physicians must be aware of medications that can precipitate hyperkalemia, how these drugs induce alterations in potassium homeostasis, and the patient characteristics that increase the risk of hyperkalemia.

Succinylcholine: adverse effects and alternatives in emergency medicine

Succinylcholine has long been the favored neuromuscular blocking agent for emergent airway management because of its rapid onset, dependable effect, and short duration. However, it has a plethora of undesirable side effects, ranging from the inconsequential to the catastrophic. When patients requiring tracheal intubation present with potential contraindications to succinylcholine use, the emergency physician will need to substitute a rapid-onset nondepolarizing neuromuscular blocking agent, such as rocuronium or mivacurium. An understanding of the pharmacology of these agents is essential.

[The use of curare-like agents in resuscitation]

OBJECTIVE

To analyse current data on use of neuromuscular blocking agents (NBA) in the intensive therapy unit (ITU) patients and to propose practice guidelines.

DATA SOURCES

We did a Medline search of French and English language articles on NBA administration in ITU patients from 1960 to 1998. Data were also selected from our own collection of articles and books.

STUDY SELECTION

Original articles, clinical cases, letters to the editor and review articles were considered.

DATA EXTRACTION

Data on pharmacology of NBA in the ITU patient were extracted, as well as data on administration patterns and cost.

DATA SYNTHESIS

The indications for myorelaxation in ITU patients include either short term use, as in anaesthesia, or long term administration for facilitation of mechanical ventilation, control of increased intracranial pressure, status epilepticus, tetanus and oxygen demand in case of muscular hyperactivity, diagnostic and therapeutic procedures facilitation. A beneficial effect of NBA on the prognosis of the disease for which these agents have been used is not yet proven. Suxamethonium, because for its short onset time and duration of action, is the agent of choice for endotracheal intubation if myorelaxation is required. Among the benzylisoquinolines, atracurium and besilate of cisatracurium are convenient agents in ITU patients, whereas mivacurium is of no special interest. Among the aminosteroids, pancuronium and vecuronium are the most often used agents in the ITU. Rocuronium has not yet been extensively assessed. Myorelaxants carry risks for morbidity and mortality. The difficulty to assess the neurological status and the level of sedation is a recognised adverse effect. An accidental disconnection from the circuit and the resulting asphyxia is nowadays recognised without delay by the ventilator. NBAs increase the rate of bronchopulmonary infections. Cardiovascular complications include extreme bradycardia or sinus arrest following vecuronium administration, and cardiac arrest after suxamethonium injection mainly in burned or traumatised patients. Conversely to anaesthesia, NBAs do not carry a significant risk for anaphylactic or anaphylactoid complications in the ITU. Tachyphylaxis occurs mainly in burns and other pathologies modifying acetylcholine receptors. Neuromuscular complications include myopathy from steroids, postparalytic syndrome, deconditioning syndrome and intensive care polyneuropathy. Prolonged curarisation after discontinuation of NBA administration has a multifactorial origin and must be differentiated from neuromuscular complications. For prolonged neuromuscular blockade, pancuronium, vecuronium and atracurium are the agents of choice. The association with an adequate sedation is essential. Assessment of depth of neuromuscular blockade is not based on clinical symptoms but on train-of-four (TOF) twitch monitoring. A convenient basic relaxation is usually obtained with the suppression of the two last responses to TOF.

CONCLUSION

The use of NBA in ITU patient should result from a rational decision making procedure, the blockade titrated with a TOF monitor and maintained as superficially and shortly as possible.

Intubating conditions provided by propofol and alfentanil--acceptable, but not ideal

BACKGROUND

The use of muscle relaxants to facilitate intubation is associated with several side effects regardless of whether depolarizing or non-depolarizing drugs are used. In the present study we compared the intubating conditions, haemodynamic responses and changes in oxygen saturation following induction with alfentanil and propofol or alfentanil, thiopental and suxamethonium.

METHODS

Eighty patients (ASA I or II) were in a double-blind manner assigned to receive either of the two induction methods. Intubating conditions were assessed on the basis of jaw relaxation, ease of insertion of the endotracheal tube and coughing on intubation. Heart rate, systolic arterial pressure and oxygen saturation were monitored throughout the procedure.

RESULTS

The use of alfentanil and propofol resulted in significantly lower scored intubation points. Systolic arterial pressure decreased and heart rate increased significantly in the alfentanil-thiopental-suxamethonium group as compared to the alfentanil-propofol group. There were no significant changes in oxygen saturation.

CONCLUSION

The results show that propofol and alfentanil in combination provides haemodynamic stability and unaltered oxygen saturation but less optimal intubating conditions.

Succinylcholine-induced hyperkalemia following prolonged pharmacologic neuromuscular blockade

While being treated for the acute respiratory distress syndrome, a 27-year-old woman developed profound hyperkalemia and cardiac arrest following the administration of succinylcholine chloride (SCh). She had none of the risk factors previously described for development of severe hyperkalemia following SCh administrations; however, she had been intermittently treated with nondepolarizing neuromuscular blocking drugs throughout the course of her illness. We suggest that immobilization of critically ill patients with pharmacologic neuromuscular blockade may predispose them to severe hyperkalemia and cardiac arrest following administration of SCh. SCh should be used with great caution in such patients.

Lack of a hyperkalemic response in emergency department patients receiving succinylcholine

OBJECTIVE

To determine whether serum potassium (K) levels increase significantly following succinylcholine (SCh)-assisted intubation in ED patients.

METHODS

A prospective, noncontrolled, consecutive case series design was used to evaluate the change in serum K levels in ED patients who received SCh for emergency intubation. The study was performed at an academic medical center staffed by board-certified emergency physicians. The subjects were 100 consecutive prescreened ED patients with various diagnoses who received SCh for intubation. The eligible subjects had serum K levels determined prior to and 5 minutes after administration of a 1.0-1.5-mg/kg i.v. dose of SCh. Serum K levels were measured by the ion-selective electrode assay method.

RESULTS

The mean change in serum K levels was -0.04 mmol/L (95% CI -0.14 to 0.06). The maximum increase was 1.10 mmol/L. The serum K level rose in 46 cases, decreased in 46 cases, and was unchanged in eight cases. No instance of SCh-induced cardiac arrest was identified.

CONCLUSION

Changes in serum K levels following SCh administration in prescreened ED patients were minimal. A hyperkalemic response is uncommon in ED patients who undergo SCh-assisted intubation.

Burn injury-induced nicotinic acetylcholine receptor changes on muscle membrane

Patients with thermal injury show pharmacological responses akin to those seen following denervation of motor nerve where there is an increase in the number of muscle-type acetylcholine receptors (AChR). This study in the rat, examined the effect of 20%, 30%, and 50% body surface area burn injury on gastrocnemius and diaphragm AChR number, quantitated by [125I]alpha-bungarotoxin (alpha-BGT). Pharmacodynamic responses to D-tubocurarine were evaluated in the gastrocnemius muscle. AChR from gastrocnemius muscle were significantly increased in all burn groups at 14 days after burn. After 28 days, the AChR had returned to control in the 20% and 30% burn groups, but persisted in the 50% burn group. AChR from diaphragm did not show significant changes between groups. Resistance to D-tubocurarine was not seen in burn groups compared with controls. Burn trauma causes increases of AChR at sites distant from the area of injury. Diaphragm muscle may be less sensitive than gastrocnemius to mediators which upregulate AChR.

Phenytoin-induced resistance to vecuronium

Chronic phenytoin therapy causes resistance to some nondepolarising muscle relaxants. We have confirmed that this resistance is seen with vecuronium and suggest that at least a week of phenytoin therapy is required for a significant effect to develop. The mechanism of this resistance is not known. We have shown that an exaggerated rise in serum potassium after succinylcholine does not occur in patients with demonstrated resistance to vecuronium from chronic phenytoin therapy. This would suggest that significant extrajunctional acetylcholine receptor proliferation is an unlikely mechanism.